Ion exchange resin containing zero-valent metal

ABSTRACT

THIS SPECIFICATION DISCLOSES AN ION EXCHANGE RESIN CONTAINING ZERO-VALENT METAL. IN THE PREPARATION THEREOF, AN ION EXCHANGE RESIN IS CONTACTED WITH A REDUCING AGENT TO FIX THE REDUCING AGENT IN THE RESIN. THEAFTER, THE RESIN IS CONTACTED WITH A SOLUBLE METAL COMPOUND, THE METAL BEING FROM GROUPS VIII, I-B, II-B, III-B, IV-B, V-B, VI-B, AND VII-B OF THE PERIODIC TABLE. THE METAL OF THE COMPOUND IS THEREBY REDUCED TO THE ZERO-VALENT STATE IN-SITU IN THE RESIN. THE RESULTING PRODUCT MAY BE EMPLOYED AS A CATALYST.

United States Patent Oifice 3,578,609 Patented May 11, 1971 3,578,609ION EXCHANGE RESIN CONTAININ ZERO-VALEN T METAL Werner O. Haag, Trenton,and Darrell Duayne Whitehurst, Raritan, N.J., assignors to Mobil OilCorporation No Drawing. Filed Oct. 2, 1967, Ser. No. 672,007 Int. Cl.C07c /02 US. Cl. 252-430 4 Claims ABSTRACT OF THE DISCLOSURE Thisspecification discloses an ion exchange resin containing zero-valentmetal. In the preparation thereof, an ion exchange resin is contactedwith a reducing agent to fix the reducing agent in the resin.Thereafter, the resin is contacted with a soluble metal compound, themetal being from Groups VIII, I-B, II-B, III-B, IV-B, V-B, VI-B, andVII-B of the Periodic Table. The metal of the compound is therebyreduced to the zero-valent state in situ in the resin. The resultingproduct may be employed as a catalyst.

CROSS REFERENCES TO RELATED APPLICATIONS Use of the catalysts in certainreactions is disclosed in our copending application Ser. No. 672,008filed concurrently herewith entitled Catalytic Polystep Reactions.

BACKGROUND OF THE INVENTION (1) The field of the invention comprisesheterogeneous catalysis with metals.

(2) The increasing demand for specialized chemicals by the plastics,chemical, automotive and other industries has created a need for thedevelopment of very selective catalysts. With catalysis by metals, theselectivity for chemical conversions is influenced by the support, metalconcentration thereon, degree of dispersion of the metal (crystallitesize), and the addition of specific poisons. By the use of ion exchangeresins as supports, as disclosed herein, the invention provides a meansof controlling these variables much more easily than has been previouslypossible. Unusual selectivity for hydrogenations has been demonstrated.

SUMMARY OF THE INVENTION The invention enables metals, particularly ofthe platinum series, but also including other metals of Group VIII, andmetals of Groups I-B, II-B, III-B, IVB, V-B, VI-B, and VII-B of thePeriodic System, to continue to be used as catalysts but provides themin an improved form by incorporating the same on and/or in insoluble ionexchange resins. The resulting catalyst material is ininsoluble inconventional liquids and functions as a heterogeneous catalyst.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS Generally speaking, in order toprepare the supported metal catalysts, an ion exchange resin inparticulate form is treated with a reducing agent so as to fix the agenteither chemically or physically to the resin without destroying thereducing properties of the agent. The treated resin is then contactedwith a suitable soluble metal compound, which is reducible, and whichmay be either an ionic or a neutral compound, and the compound isreduced on contact with the reducing agent and deposits zero-valentmetal on the resin at or near the site formerly occupied by the reducingagent.

palladium deposits on the outer surface of the particles in the form ofa thin shell.

On the other hand, if the hydrazine-treated resin is held in aqueoussuspension for a prolonged period of time, a redistribution of thehydrazine throughout the resin particles is obtained, and thisredistribution is accelerated by applying heat, as refluxing. Thehydrazineloaded resin can be used to reduce solutions of metal compoundsto produce catalysts with a variety of metal dispersions, ranging from acatalyst having metal dispersed in the form of a shell (thicker than inthe preceding example) adjacent the exterior boundary of the particlesto a catalyst in which metal is dispersed uniformly throughout theparticles. Factors in obtaining various dispersions are the rates ofdiifusion of the metal compounds into the porous particles and the ratesof reduction of the metal compounds by the hydrazinium ions which arefixed in the resin. Metal compounds which diifuse relatively slowly intothe particles but which are relatively rapidly reduced will depositmetal almost exclusively on or adjacent the outer surface of theparticles; while less reactive and more diffusable metal compounds leadto more uniform dispersions of metal inthe particles.

The porous ion exchange resin which is used to prepare the catalystmaterial contains functional groups, i.e. acid groups in the case of acation exchange resin and basic groups in the case of an anion exchangeresin, and these groups of course are chemically bonded to the resin orresin matrix. Cation exchange resins contain such acidic functionalgroups as sulfonic acid, phenolsulfonic acid, phenol, phosphonic acid,carboxylic acid, etc. Anion exchange resins contain such basic groups asprimary, secondary, tertiary amine, or quaternary ammonium groups, andthese may be aliphatic, aromatic, heterocyclic, or cycloalkane amines;or mixtures thereof, or diamines, triamines, and alkanolamines; oramines like alpha, alphadipyridyl; or the resins may contain basicgroups like guanidine, dicyandiamidine, nitrile, cyanate, isocyanate,thiocyanate, isothiocyanate, isocyanide, etc., as well as other organicnitrogen-containing groups. These ion exchange resins are generally madeby subjecting to appropriate chemical treatment a desired copolymer basematerial or matrix; for example, a styrene-divinylbenzene copolymer maybe converted to a sulfonic acid cation exchange resin by sulfonation; orthe resins may be made by reacting all ingredients together, thus acation exchange resin of phenolic type can be prepared by reacting aphenol, an aldehyde, and a sulfonic acid. Illustrative ion exchangeresins for making the catalysts include sulfonated copolymers of styreneand a divinyl-aromatic; phenolic methylene sulfonic acid resins;sulfonated coal; styrene-divinylbenzene copolymer containingdimethylaminomethyl groups; polystyrene sulfonic acid resins;cross-linked polyvinyl pyridine; a copolymerized mixture of phenol,formaldehyde, and triethylenetetramine; hydroylzedstyrene-divinylbenzene copolymers incorporating maleic anhydride;polyacrylic acid resin; chloromethylated styrene-divinylbenzenecopolymer treated With trimethylamine; melamine formaldehyde guanidinepolymers; urea-formaldehyde-triethanolamine resins;polyalkylene-polyamine-formaldehyde resins, etc. Ion exchange cellulosesare suitable. Preferably the resin is in particulate form, particularlybead form, and may have any desired particle size. The resin is porousunder the reaction conditions employed. Thus, the resin may beintrinsically porous or may have induced porosity, such as achieved, forexample, by the swelling of a nonporous metal compound containing resinin a reaction solvent.

The reducing agent may be any suitable compound capable of being fixed,either chemically or physically, on and/ or in the resin withoutdestruction of its reducing power. For example, it may be hydrazine, asubstituted hydrazine, hydroxylamine, a mercurous compound, or a cuprouscompound, all of which are capable of being chemically bonded to cationexchange resins while maintaining their reducing properties. Or it maybe a formate, hydrosulfite, or hypophosphite, e.g. sodium or potassiumhypophosphite, which may chemically bond to an anion exchange resinwhile maintaining their reducing properties. Stannous compounds likestannous chloride also form chemical compounds with ion exchange resinswithout losing reducing power. Other agents include hydroquinone,ferrous oxalate, pphenylenediamine, p-aminophenol, catechol, pyrogallol,and the like.

The metal compound may be any suitable ionic or neutral compound whosemetal moiety is one selected from the metals of Groups VIII, I-B, II-B,IIIB, IV-B, V-B, VI-B, and VIIB of the Periodic System. For example,ionic compounds may include copper sulfate, ferric chloride, nickelacetate, silver nitrate, gold chloride, mercuric acetate, cadmiumnitrate, sodium tetrachloropalladite (II), azidopentaamminecobalt (III),sulfate, hexaaquochromium (III), chloride, potassiumtetranitritoplatinate (II), potassium hexaiodo rhenate (IV), biscyclopentadienyl iridium (III) chloride, and cesiumaquoethyltrichlororhodiate (III). Illustrative neutral compounds arebis(benzonitrile) palladium dichloride, bis(hydrogen sulfito)tetraarnmineruthenium, cis-dichlorobis(triethylphosphine)platinum (II),tetra(pyridine)platinum (II) tetrachloroplatinate (II),cyclooctadieneplatinum dibromide, ruthenocene, ar-allyl nickel bromide,tetraethyl lead and bisbenzene chromium.

It will be understood that the choice of metal compound may influencethe choice of the reducing agent. For example, platinum compounds workwell with reducing agents like hydrazine and formates. With ironcompounds it is preferred not to use an agent like hydroxylamine; andwith iron, cobalt, and nickel compounds it is preferred not to useformates. Hydrazine is generally useful for most metal compounds. Asimple test is suflicient to indicate the choice of reducing agent withany particular metal compound.

To prepare the catalyst material, the desired ion exchange resin istreated with the reducing agent at a temperature which is generally roomtemperature but which may range to about 100 C. or to refluxing. Theagent may be in vaporous or liquefied form; in the latter case the agentmay either be normally liquid or, if a solid, in solution in a suitablesolvent. The solvent may be an ionizing compound like water and variouslow molecular weight alcohols, or a non-ionizing compound like ahydrocarbon, chlorinated hydrocarbon, ether, etc. The time of contact isvariable, depending on the type of metal deposition desired in the resinparticles, i.e. shells of varying depth or a uniform depositionthroughout the particles. Generally, to obtain shell deposition, thecontact time is of the order of minutes, while for complete uniformdeposition the time is of the order of several hours.

After treatment with the reducing agent, the treated resin may bewashed, and if desired may be stored until the time of use of thecatalyst material, even for a period of weeks or months, at which timeit is mixed with a solution of the desired metal compound. For ionicmetal compounds, a polar solvent is preferred, such as water, alcohols,dimethylsulfoxide, sulfones, acetonitrile, acetone, etc.; and forneutral metal compounds a non-polar solvent is preferred, such as ahydrocarbon, chlorinated hydrocarbon, ether, etc. The metal compound isreduced on contact with the reducing agent, and zero-valent metal isdeposited at or near the site of the reducing agent.

4 Thereafter the resin particles are suitably washed and dried.

It is found that with a reducing agent like hydrazine, shell typedeposition of metal on the resin particles or beads usually takes placewhen the hydrazine contact time is short, the temperature is roomtemperature, and a nonpolar solvent like chloroform, benzene, or etheris used to dissolve the hydrazine. Deposition in depth is usuallyobtained by using a long hydrazine contact time, a higher temperaturegoing up to refluxing, and an ionizing solvent like water or an alcohol.These conditions and results generally apply to other reducing agentsbesides hydrazine, including substitued hydrazines, formates, andnonsalt agents, i.e. those which are neutral with respect to charge.

Not only may the degree of dispersion of metal particles in the resin becontrolled, but also the amount of metal, which may range from 0.01 or0.1% to l, 5, 10% or more, and even up to 50% or more, weight basis. Ofparticular significance from an economic view is the fact that there isno waste of metal during the metal deposition step, metal deposits onlyon or in the resin and not in the exterior solution.

The catalyst materials are suitable for use in reactions generallycatalyzed by metal catalysts, preferbly in reactions where lowertemperatures prevail, say up to 200 or 250 C. and preferably too inliquid phase reactions. They are particularly useful in hydrogenationreactions, as illustrated in Example 2, involving compounds havingcarbon-to-carbon unsaturation, as in the conversion of acetylenes,olefins, and diolefins, using catalyst materials containing platinum,palladium, ruthenium, rhodium, cobalt,-and other metals.

Other catalytic reactions in which the catalysts are of value includedecarbonylations, and deuterium-hydrogen exchange reactions such asexchange between deuterium gas and Water to produce heavy water or anexchange between deuterium gas and aromatic hydrocarbons. Otherreactions include the oxidation of hydrocarbons; for example, ethylenemay be oxidized in solution in a polar solvent to give useful products;thus, with an aqueous solvent, the product is acetaldehyde; withmethanol as solvent, the product is vinyl methyl ether; and with aceticacid as solvent, the product is vinyl acetate. Hydrocarbons and othercompounds may be dehydrogenated. Carbon monoxide may be oxidized withoxygen in a CO-re moval reaction. The catalysts are further useful infuel cell electrodes to catalyze the oxidation of various fuels,including hydrocarbons; and they are suitable in other electrochemicaloxidations and in reductions.

With some catalyst materials, prepared as described, the functionalgroups, such as sulfonic acid or trimethylbenzylammonium hydroxide ofthe resins may be regenerated by appropriate treatment. For example, inthe case of Amberlyst-IS, a cation exchange resin comprisinga"styrene-divinylbenzene copolymer containing sulfonic acid groups, thesulfonic acid groups may be regenerated, after the step of metaldeposition, by treatment of the catalyst with an acid such ashydrochloric acid; the regenerated material contains tree sulfonic acidgroups and also has metal particles dispersed in and on the resin; it isuseful as a dual functional catalyst, i.e. one containing two types ofsites, acid sites and metal sites, and is able to catalyze organicpolystep reactions. In such reactions, as described in our copendingapplication Ser. No. 672,008, filed concurrently herewith, entitledCatalytic Polystep Reactions, one type of site catalyzes a reaction stepdifferent from that catalyzed by another type of site. Depending on theion exchange resin, acid or basic sites may be present, together withthe metal sites. Thus, with a resin like Amberlyst A-27, comprising astyrenedivinylbenzene copolymer containing trimethylbenzylammoniumgroups, the regenerated material would have basic sites as well as metalsites. It should be understood that the choice of regenerating reagentis determined by the metal which is deposited within the resin as wellas functional groups of the resin which are to be regenerated. Forexample, a sulfonic acid resin, in a non-acid form, containing depositediron should be regenerated by dilute solutions of sulfuric acid ratherthan dilute hydrochloric acid as the latter would tend to remove some ofthe metallic iron.

Regeneration may not be necessary in instances where the resin has beenexchanged to less than its capacity by reducing agents and metal ions asthe final product would still have active acidic or basic groups.

Although low temperature liquid phase reactions are preferred, it willbe appreciated that many low temperature reactions involve gaseousreactants and may be carried out in the gas phase, and the invention isapplicable to these reactions. In some reactions, both liquid andgaseous reactants take part and are suitably catalyzed by the presentcatalysts. In all reactions, ease of catalyst separation by conventionaloperations of filtration, decantation, or centrifugation is acharacteristic, whether the products and/or reactants are liquid orgaseous. The reactions may be carried out in conventional fixed bed flowreactors, or continuously stirred flow reactors, or in batch reactors.

Other useful catalyst materials, comprising modifications of thosedescribed, may be made by first treating the starting ion exchange resinwith an appropriate reagent to introduce thereto one or more additionalfunctional groups, such as amine, phosphine, arsine, stibine, sulfide,and the like. Or in place of the ion exchange resins, organic polymersmay be used that contain the last-mentioned functional groups.

The invention may be illustrated by the following examples.

EXAMPLE 1 About 23 g. Amberlyst-IS (a cation exchange resin comprising astyrene-divinylbenzene copolymer containing sulfonic acid functionalgroups) was suspended in 250 ml. absolute ethanol, the suspensionstirred, and 2 ml. of 64% aqueous hydrazine added. Stirring wascontinued for minutes at room temperature, after which time the exteriorsolution still contained some hydrazine. The solids were then separatedby filtration and washed well with ethanol; they comprised resincontaining chemically bound hydrazine. They were suspended in 150 ml.absolute ethanol, the suspension stirred, and to it were added 200 ml.of a solution of 1.0 g. bis-(benzonitrile)-dichloropalladium (H)dissolved in absolute ethanol. The mixture was refluxed for 1 hour,during which time the solution became colorless while the resinblackened owing to the deposition of palladium metal. The solids werefiltered, washed consecutively with ethanol, water, 6 N HCl solution, 2N HCl solution, water, ethanol, and ether, and then dried in an oven at110 C. The resulting catalyst beads, when cut in half, were observed tohave palladium metal incorporated as a thin shell on the exteriorboundary of the beads. Chemical analysis showed 3% palladium to bepresent, and 4.25 milliequivalents of sulfonic acid groups per gram ofresin.

6 EXAMPLE 2 The catalyst of Example 1 was used for catalyzing thehydrogenation of l-hexyne. About 200 mg. of the catalyst were finelyground and suspended in 25 ml. methylcyclohexane solvent. While themixture was stirred, hydrogen at 1 atmosphere was introduced and 5 ml.of 1- hexyne was injected into the mixture. Hydrogen consumption wasobserved, and the mixture analyzed periodically by vapor phasechromotography. After 20 minutes of reaction, analysis showed nol-hexyne present, 95% 1- hexene, and 5% n-hexane. After minutes, therewere present 50% l-hexene, 20% 2- and 3-hexenes, and 30% n-hexane. Thus,the catalyst promoted hydrogenation of 1- hexyne and l-hexene andisomerization of l-hexene.

In contrast to such action, a conventional palladium on charcoalcatalyst afiords faster hydrogenation of l-hexene to hexane thanhydrogenation of l-hexyne to l-hexene. This makes isolation of theolefin diflicult. The catalyst used herein promotes hydrogenation ofl-hexene to hexane at a much slower rate than it promotes thehydrogenation of l-hexyne to l-hexene. It is thus more selective andallows easier isolation of the olefin.

The Periodic Table classifications as used herein are based on thearrangement distributed by E. H. Sargent & Co. and further identified bythe legend Copyright 1962 Dyna-Slide Co.

It will be understood that the invention is capable of obviousvariations without departing from its scope.

In the light of the foregoing description, the following is claimed:

1. The method which comprises contacting an ion exchange resin with areducing agent to fix said reducing agent in said resin, then contactingsaid resin with a soluble metal compound, the metal of which is selectedfrom Groups VIII, I-B, II-B, III-B, IV-B, V-B, VI-B, and VII-B of thePeriodic Table at a temperature sufiiciently high to reduce said metalof said metal compound to zero-valent metal, thereby reducing said metalof said metal compound to zero-valent metal in situ in said resin oncontact of said compound with said reducing agent and depositing saidzero-valent metal in said resin, and recovering as product said resincontaining said zero-valent metal.

2. Method of claim 1 wherein said metal is a platinum series metal.

3. Method of claim 1 wherein said resin is an anion exchange resin.

4. Method of claim 1 wherein said resin is a cation exchange resin.

References Cited UNITED STATES PATENTS 2,861,045 11/1958 Langer 2524303,417,066 12/1968 Corte et al. 26O96 3,442,924 5/1969 'Imura et al252-431X 3,442,954 5 1969 Crocker et a1 252-431X PATRICK P. GARVIN,Primary Examiner US. Cl. X.R.

